Require Sender Authentication Enabled even we received mail to DL from anonymous users in exchnage 2007 SP3

Hi, You need to check Authenticated users in DL properties under the tab Mail flow setting->Message delivery restriction->required all sender are authenticated, if you want to enable for whole organization have a look into this post: http://social.technet.microsoft.com/Forums/en-US/exchangesvrsecuremessaging/thread/8f627511-8d7f-4eb0-ac5f-efb86e7f9a0bRipu Daman Mina | MCSE 2003 & MCSA Messaging